The present invention relates to a digital-signal processing apparatus and is applicable to equipment such as a mini-disc recording/playback apparatus. The present invention allows the amplitude of a digital signal recorded on a recording medium to be adjusted through simple processing carried out in a simple configuration to rewrite only first coefficient data prescribing the amplitude of the digital signal or first coefficient data prescribing the amplitude of a component obtained as a result of conversion of the digital signal.
Traditionally, in a mini-disc recording/playback apparatus, an audio signal is subjected to data compression adopting an ATRAC (Adaptive Transform Acoustic Coding) technique at predetermined time intervals prior to recording the compressed data onto a mini-disc adding further information including error-correction codes added to the data.
For the reason described above, in processing such as fade-in or fade-out carried out on the audio data recorded on the mini-disc, the mini-disc recording/playback apparatus reproduces encoded data from the mini-disc and decompresses the reproduced data to generate audio data. The reproduced audio data is further multiplied by a gain coefficient, subjected to data compression and again recorded onto the mini-disc.
In addition, in the case of adopting SCMS (serial copy management system), direct recording of audio data is controlled and restricted by an SCMS, the mini-disc recording/playback apparatus once converts decompressed audio data into an analog signal. Subsequently, the level of the analog signal is corrected before the analog signal is converted into a digital signal, or multiplied by a gain coefficient after being converted into the digital signal. Then, audio data obtained as a result of the multiplication is subjected to compression before being recorded onto the mini-disc.
In order to change the volume of audio data recorded on the mini-disc as described above, this sort of system requires a data-decompression circuit for decompressing audio data played back from the mini-disc and a data-compression circuit for compressing audio data with the volume thereof changed, raising a problem of a configuration becoming complicated accordingly. In order to solve this problem, there is a conceivable processing circuit with a high processing speed whereby the data compression and the data decompression can be carried out concurrently at the same time. In this case, however, there arises another problem of a complicated processing procedure of the processing circuit.
In either case, another mini-disc is required separately for recording the audio data with the volume thereof adjusted. In addition, it is also necessary to reproduce an entire song or data from the entire mini-disc even if the volume merely needs to be changed partially.
It is thus an object of the present invention addressing the problems described above to provide a digital-signal processing apparatus that is capable of adjusting the amplitude of a digital signal recorded on a recording medium by carrying out simple processing in a simple configuration.
In order to solve the problems described above, the present invention selectively updates first coefficient data prescribing the amplitude of a digital signal or first coefficient data prescribing the amplitude of a component obtained as a result of conversion of the digital signal, and second coefficient data prescribing the waveform in conjunction with the first coefficient data.
By selectively updating the first coefficient data prescribing the amplitude, the level of a digital signal can be changed without the need of decoding the digital signal. As a result, the level of the digital signal can be changed by carrying out simple processing in a simple configuration.